102 
Journal of the Mitchell Society 
[November 
set to 160°. At this temperature, the viscosity is diminished suf- 
ficiently to enable a complete distillation to be carried out without 
frothing. During the latter part of the summer, however, and 
during the autumn, the amount of this mucilaginous substance 
evidently increased, and to such an extent that it became practic- 
ally impossible to distil off the volatile oil. Partial success was 
secured by he addition of concentrated sodium hydroxide solution 
to the distilling flask. 
The resin left after distillation is pale yellow, similar to the best 
grades of commercial resin. Acid number 167. 
The volatile oil, freed from water by standing in contact with 
calcium chloride, was a limpid liquid with a fragrant odor sug- 
gesting at once the presence of limonene. The physical constants 
of the oil follow : 
Sp. gr.: 20°, 0.8478. 
Sp. rotation: 20°, — 105° 36. 
Index of refraction: 20°, 1.4734. 
Acid number: 0. 
Saponification number: 1.54. 
Iodine number: 378. 
Solubility in ethyl alcohol at 22.5° : 
95 per cent, alcohol 1.35 parts required to dissolve 1 part of volatile oil. 
90 per cent, alcohol 4.80 parts required to dissolve 1 part of volatile oil. 
85 per cent, alcohol 8. 10 parts required to dissolve 1 part of volatile oil. 
80 per cent, alcohol 16.20 parts required to dissolve 1 part of volatile oil. 
70 per cent, alcohol 56.00 parts required to dissolve 1 part of volatile oil. 
Comparative evaporation with the volatile oil of P. palustris, at 
room temperature, in shallow watch glasses, 0.2 gram of each 
used. 
P. palustris P. serotina 
Time Per cent. Per cent. 
Loss after % hour 35.7 
Loss after 1 hour 62.5 
Loss after 1)4 hours \ 91.7 
Loss after 2 hours 96.0 
Loss after 5 hours 97.8 
20.30 
37.30 
53.40 
68.47 
98.80 
On fractionation the following results were obtained: 
